Webasto 3900 Heater

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  • #5701
    Moderator
    Keymaster

    Kenneth of Stella Scot asked in another thread if we have a heater installed. The answer is yes, we have a Webasto 3900. We installed it last year. The installation was easier because Rainshadow in past years had a Webasto installed, so all the ducting was already there. We just needed to add the unit, which we placed immediately aft of the rudder post.
    We are generally happy with it. The long duct runs to the forward cabin mean that the forced air flow is not as impressive as we would like. There is a lot of drag down the long duct runs. But it does heat the boat nicely. It takes about 30 minutes to heat the boat 45F to 60F.
    The combustion air intake comes from the aft cabin, and it’s quite loud when it runs.
    For one season, we had a portable propane heater (model was reportedly safe for indoor use with suitable ventilation). Propane heat was very wet – we paid the big bucks for the Webasto really to have the dry heat source. The convenience was the bonus that came with the dry heat source. We bought a thermostat, but we generally use the thermostat as a on/off switch. Once the cabin is warm, we just turn the heater off.
    Glad to answer other questions if others interested. Our installation was a bit odd because it was a retrofit, rather than a new install.
    Cheers- Marilyn and Van

    #11261
    Ronar M
    Participant

    We have an Eberspacher heater on Ronar M. Sounds a lot like the Webasto on Rainshadow; also installed in the lazarette and also a hot air system. We have outlets which we can adjust (sliding baffles) so we can shut or partially shut the air off in the after cabin closest to the heater so getting more air and heat forward to the saloon and forecabin.
    I would say we have spent more money on this heater than on anything else on board. It kept going wrong and the main agents in our area charged a fortune for everything but never made it reliable. In the end I took it to a truck company (they are used a lot in trucks) and they said ‘no wonder – you have the wrong diesel pump’ (not spotted by the main agents). With the correct pump it has worked like a dream.
    One other thing. I’m not sure how well known it is that this type of heater does not like marine diesel which tends to have too high a sulphur content. I have installed a 20L jerry can in the lazarette (held with bungy cords against the bulkhead) and use this to fuel the heater with low sulphur road diesel – more expensive but useage is relatively low. There is the added advantage that the pump is not trying to drag fuel all the way from the main diesel tank under the saloon. Cheers, Trevor

    #13351
    Voltair
    Participant

    That’s ironic – you using DERV fuel for heating and Red for driving! We too have an Eberspacher 3kw unit which worked fine until we caught diesel bug in Norway. The season after that the tubular sintered bronze filter-wick thingy that surrounds the igniting hot pin got bunged up with what I took to be coked on bio-debris. I changed that and it has worked fine for a couple of years. However, we recently had another bout of “green jelly” in the tank, so we may have probs when we start using the heater again. With the boat in Portugal at the mo, this may not be for a while!

    #13361
    Voltair
    Participant

    Thinking about your point regarding pulling fuel up from the main tank, I installed an outboard motor squeeze-me in the fuel line just under the aft basin fitting. This has a one-way valve in it, which stops the fuel running back if you have any air leaks. Since we tend to have been sailing in places where Eberspacher engineers can’t easily be found, we also uprated our controller to the digital one where you can cancel all the fault codes….. no more “3-strikes and you’re out” anymore now. Unfortunately we only did this AFTER we had paid a Swedish one to fail to cure the ignition problem that I later cured myself.

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